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 Carter YF Rebuild, Application for a 2756S
Dave Pete
Posted: Feb 18 2012, 10:41 AM


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Joined: 22-February 09



Anybody know what make/model vehicle a Carter YF 2756S was used on?

I'm rebuilding the unit on Lil Willy. It is a Franken-Carb I put together from two carbs seven years ago before I knew that it was a bad thing to do (recently been reading great older discussions from oldtime).

I probably (you know, age and memory) did it because the fuel bowl of the 2756S looked in better condition than the now "spare bowl" (currently 2600 miles away in Wyoming). I suspect the spare bowl was a 938SA due to the other parts I find in my existing unit.

Here's the stats:

2756S Fuel Bowl: the pump discharge air-bleed is closer to .031 (like on a 923SD) than it is .025 (like on a 938S, SA, SC). I say "closer to" because I had to use increasing numbers of twisted copper strands to obtain an object to measure.

The main question on the bowl is "What other internals: passageways, etc. MIGHT make this bowl uncompatible with conversion of this carb to a 938SD by changing the jet and metering rod"? Or even more specifically, "What jet and rod should be in this fuel bowl to make a proper carb for our CJ3B demands"?

Current Main Jet: 120-155, bore aprox .088 (no adverse wear signs)

Current Metering Rod: 75-996 Power .045 X .224, Mid .062-.066 X .419, Econo .071 X .808 (no adverse wear signs)

According to Ken's previous discussion comments these are both standard for a 938SA

Incidentily, I DO have the proper size fuel valve and it is the spring loaded type.

The current carb configuration (Air bleed .031, Jet 120-155, Rod 75-996) has caused a carb that has always felt just a bit rich, and a bit of stumble on acceleration. I've never really been impressed with performance or mileage and have always suspected it was set up for sea level (standard) and wanted to re-jet it for my most common elevation, about 5000'-10,000'. However, in it's current set-up, it has taken me from sea-level to 13,000' and with little noticible difference! I'm currently at 0'-5000', but within less than a year will be back into 3000'-13000'.



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Dave Pete
Casper, WY USA
1954 CJ3B
Top
oldtime
Posted: Feb 18 2012, 04:52 PM


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Evidently the Carter YF 2756s was used for Kaiser Hurricane industrial applications around 1958.
That implies that the carburetors restrictions and its air bleed orfices should be close if not exact for your particular engine.

Because your carburetor is an admixture of YF components I suggest you first verify all components used.
Upon observation of the Carter YF you will notice that it consists of 3 main sections.

1] The Air Horn assembly (top cover) is identified with Carter #6-1657 embossed near the fuel inlet.

2] The Body assembly (fuel well) is identified with Carter #1538 embossed onto the narrow end of the well.

3] The Throttle Body assembly (body flange) is identified with Carter #1-630 embossed onto the iron casting.

If you find otherwise please indicate.
I will address sea level and high altitude fuel metering specifics after you veriify the 3 castings.

In the meantime....
Can someone possibly scan and post the USM article titled Correcting Accelerator Flat Spot with fig. #10245.
The best reference for this is the 1960 SM 1002 R-3 but any USM after 1958 should suffice.


--------------------
1953 TRANS-VINTAGE CJ-3B / AC 4693 fuel pump / YF 938 SD / Hurricane / 9-1/4" Auburn clutch / T90-C / 2.46 ratio D-18 / Warn O.D. / 5.375 final drive / Powr Lok Front + Rear / Dualmatic drive flanges / deluxe Koenig half cab / 12 volt generator
2nd full re-build using the best from all vintages of CJ-3B

1964 OPTIONAL-STOCK CJ-3B Tigertop / Transport yellow (orange)
Currently serving as my one and only DAILY DRIVER

St Louis
Top
Dave Pete
Posted: Feb 18 2012, 09:25 PM


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Posts: 199
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Joined: 22-February 09



Thanks Ken. Yes indeed, all three sections are identified with those numbers.


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Dave Pete
Casper, WY USA
1954 CJ3B
Top
Doug
Posted: Feb 18 2012, 11:20 PM


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Here is the best I can do right now. It's from SM-1002-R5 dated 1965.

user posted image

user posted image


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1963 CJ3B - F134 Hurricane, T-90C, D-18, 5.38s, Overdrive, 938YF, 12V alternator
1969 Bronco - 302, 3sp, D-20
My YouTube Channel Photobucket
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Dave Pete
Posted: Feb 19 2012, 09:27 AM


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Joined: 22-February 09



Thanks Doug, that's good info, not the least of which is the side profile image of the air bleed passage-way and jet.

It was my uneducated assumption the bore was a passageway only, and because of that, it's possible I measured the passage way and not the jet bore (it was easier to insert twisted strand from below than above, very imprecise to say the least).

Later, I will attempt to measure the bore of the air bleed jet and therefore will know definitively what the 2756S air bleed is. Better run over and get some small drill bits tomorrow.

Because of Ken's good info about the 2756S's application (1958), it is close enough to, but before the beginning use of the 938SD (late 1959) to argue the 2756S could be either .025 OR .031.

Incidentily, my air bleed consists of the ball, weight and small spring-like retainer as opposed to the 938SD's air bleed needle.


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Dave Pete
Casper, WY USA
1954 CJ3B
Top
oldtime
Posted: Feb 19 2012, 02:17 PM


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My Kaiser industrial engine books do not mention the YF 2756S.
I found this reference using internet search:
http://carbkitsource.com/carbs/catalog/K/K...rial-index.html

You might try to mike some mono filiment and use that for measuring various orfices.


--------------------
1953 TRANS-VINTAGE CJ-3B / AC 4693 fuel pump / YF 938 SD / Hurricane / 9-1/4" Auburn clutch / T90-C / 2.46 ratio D-18 / Warn O.D. / 5.375 final drive / Powr Lok Front + Rear / Dualmatic drive flanges / deluxe Koenig half cab / 12 volt generator
2nd full re-build using the best from all vintages of CJ-3B

1964 OPTIONAL-STOCK CJ-3B Tigertop / Transport yellow (orange)
Currently serving as my one and only DAILY DRIVER

St Louis
Top
Dave Pete
Posted: Feb 19 2012, 02:33 PM


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Group: Members
Posts: 199
Member No.: 481
Joined: 22-February 09



I found reference to it on Mike's Carburetors...

http://www.carburetor-parts.com/

It is listed for kit #1111 which includes the 938S, SA, SC and SD. Mike's kits include two types of fuel valves (one with the spring) plus he has some good technical info and some pretty fun to watch video smile.gif Mike seems like a real nice character. He also includes an air-bleed weight since many people lose these.
I like what I've found here.

Ken, like I told Doug (prev post) I need to really verify the air-bleed jet measurement before I can determine if my main jet/metering rod are acceptable. That should determine whether I have the pre or post acceleration stumble solution carb. (Good idea on the monofiliment)

Here's another couple good links on Mike's Carbs

http://www.carburetor-parts.com/v/vspfiles...a_bulletin.jpeg

https://www.carburetor-parts.com/Articles.asp?ID=330


--------------------
Dave Pete
Casper, WY USA
1954 CJ3B
Top
oldtime
Posted: Feb 19 2012, 02:36 PM


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Group: Co-Admin
Posts: 4,556
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Joined: 12-July 08



QUOTE
"What other internals: passageways, etc. MIGHT make this bowl uncompatible with conversion of this carb to a 938SD by changing the jet and metering rod"?

As previously stated I expect the 2756S body to be compatable if not identicle.
That said all calibrated orfices remain in question without the aid of a CARTER MASTER CATALOG

High Speed Circuit figure # 10843
#1 nozzle
Accelerating Pump Circuit figure # 10844
#11 vacuum bleed passage
Low Speed Circuit figure # 10845
#6 idle air bleed
#7 air bypass
#8 economizer

Be carefull if you plan to follow Mikes video. It is a generic reference that not specif for a particular model.
1 Example: the 938SD uses an aluminum check ball and not steel as indicated in his video.


--------------------
1953 TRANS-VINTAGE CJ-3B / AC 4693 fuel pump / YF 938 SD / Hurricane / 9-1/4" Auburn clutch / T90-C / 2.46 ratio D-18 / Warn O.D. / 5.375 final drive / Powr Lok Front + Rear / Dualmatic drive flanges / deluxe Koenig half cab / 12 volt generator
2nd full re-build using the best from all vintages of CJ-3B

1964 OPTIONAL-STOCK CJ-3B Tigertop / Transport yellow (orange)
Currently serving as my one and only DAILY DRIVER

St Louis
Top
Dave Pete
Posted: Feb 19 2012, 02:53 PM


Member


Group: Members
Posts: 199
Member No.: 481
Joined: 22-February 09



Yes, videos very generic, if not entertaining smile.gif

Thanks very much for the return to the original concern. What is meant by these figure's and #'s?

High Speed Circuit figure # 10843
#1 nozzle
Accelerating Pump Circuit figure # 10844
#11 vacuum bleed passage
Low Speed Circuit figure # 10845
#6 idle air bleed
#7 air bypass
#8 economizer

I suppose the #'s are items in the figure's?


--------------------
Dave Pete
Casper, WY USA
1954 CJ3B
Top
oldtime
Posted: Feb 19 2012, 02:58 PM


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Group: Co-Admin
Posts: 4,556
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The figures are Willys Motors pics providing numbered references.
They are found in the various Universal Service Manuals (USM's).
Sorry, as you know I have zero capability to upload any pics.

Your previously verified casting numbers are correct for all YF 938 applications however...
The Carter Master Catalog is the only source available to specify exactly how the YF 2756S Body was machined concerning the various orfice restrictions.


--------------------
1953 TRANS-VINTAGE CJ-3B / AC 4693 fuel pump / YF 938 SD / Hurricane / 9-1/4" Auburn clutch / T90-C / 2.46 ratio D-18 / Warn O.D. / 5.375 final drive / Powr Lok Front + Rear / Dualmatic drive flanges / deluxe Koenig half cab / 12 volt generator
2nd full re-build using the best from all vintages of CJ-3B

1964 OPTIONAL-STOCK CJ-3B Tigertop / Transport yellow (orange)
Currently serving as my one and only DAILY DRIVER

St Louis
Top
Dave Pete
Posted: Feb 19 2012, 03:22 PM


Member


Group: Members
Posts: 199
Member No.: 481
Joined: 22-February 09



QUOTE
My Kaiser industrial engine books do not mention the YF 2756S.
I found this reference using internet search:
http://carbkitsource.com/carbs/catalog/K/K...rial-index.html


Interestingly, at the same place, under "See Kaiser Auto and Truck for more listings" I found this...

http://carbkitsource.com/carbs/catalog/Jeep/index.html

indicating the 2756S was used on a 1950-67 Forward Control Willys Jeep (FC-150) which just happens to be what I seem to remember my Jeep seller telling me was the application of the extra engine that came with my CJ3B. Have we solved the mystery? Is the 2756 found under '50-'67 FC-150 in your Carter Master Catalougue?


--------------------
Dave Pete
Casper, WY USA
1954 CJ3B
Top
oldtime
Posted: Feb 19 2012, 03:33 PM


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Group: Co-Admin
Posts: 4,556
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Joined: 12-July 08



I don't have a Carter Master Catalog, so I can't verify orfice calibrations for various carburetor models.
If you guys all wanna send me about $500 to $1000 bucks I might be able to locate one with ample luck. ohmy.gif
That said I do own virtually all the USM's and UPL's.
I only have 1 FC maual and its the earliest one. It is dated 1957 .
It does not mention the YF 2756S for FC applications.
My gut instinct tells me the main and perhaps the only difference between the the YF model 2756S and the 938S is likely to be the design of the air horn casting.

The Carter YF was in a constant state of progression.
The 1950 to 1967 dating is another generic reference.
The various models were not available for each of those years as is indicated.


--------------------
1953 TRANS-VINTAGE CJ-3B / AC 4693 fuel pump / YF 938 SD / Hurricane / 9-1/4" Auburn clutch / T90-C / 2.46 ratio D-18 / Warn O.D. / 5.375 final drive / Powr Lok Front + Rear / Dualmatic drive flanges / deluxe Koenig half cab / 12 volt generator
2nd full re-build using the best from all vintages of CJ-3B

1964 OPTIONAL-STOCK CJ-3B Tigertop / Transport yellow (orange)
Currently serving as my one and only DAILY DRIVER

St Louis
Top
Dave Pete
Posted: Feb 19 2012, 03:40 PM


Member


Group: Members
Posts: 199
Member No.: 481
Joined: 22-February 09



Well thanks very much for the good info, and I'll keep you advised as I go through this.


--------------------
Dave Pete
Casper, WY USA
1954 CJ3B
Top
Dave Pete
Posted: Feb 19 2012, 08:25 PM


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Group: Members
Posts: 199
Member No.: 481
Joined: 22-February 09



Okay so I did verify the pump air-bleed is .031.


--------------------
Dave Pete
Casper, WY USA
1954 CJ3B
Top
oldtime
Posted: Feb 20 2012, 11:11 AM


MODERATOR


Group: Co-Admin
Posts: 4,556
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Joined: 12-July 08



One possible problem is that Main Jet: 120-155, and Metering Rod: 75-996
were not calibrated to work with the .031 accelerator pump discharge jet.
Reference: article F-27.


--------------------
1953 TRANS-VINTAGE CJ-3B / AC 4693 fuel pump / YF 938 SD / Hurricane / 9-1/4" Auburn clutch / T90-C / 2.46 ratio D-18 / Warn O.D. / 5.375 final drive / Powr Lok Front + Rear / Dualmatic drive flanges / deluxe Koenig half cab / 12 volt generator
2nd full re-build using the best from all vintages of CJ-3B

1964 OPTIONAL-STOCK CJ-3B Tigertop / Transport yellow (orange)
Currently serving as my one and only DAILY DRIVER

St Louis
Top
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